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Are you curious about your baby's development? Then this weight percentile calculator is designed exactly for you! You'll learn in which percentile your child places, how that relates to their peers, and, most importantly - how baby weight percentiles can describe a child's health from birth. That's not all - in the article below we explain why we use percentiles, how to interpret the WHO growth chart, and we'll show you a quick example of how this infant growth chart calculator is used.

So, if you've ever asked yourself "what percentile is my baby?", stay with us and read on.

The aim of the baby weight chart

When assessing a baby's weight, a percentile scale is used. As most children have a specific time where they grow rapidly, require more calories and reach many developmental milestones, it's not easy to know what your child should weight at any particular age.

Therefore, the WHO has developed a baby weight chart, which describes the typical trajectory of a kid's development. With this infant growth chart, you don't look solely at how much they weigh, their height, or their BMI, but where among their peers the child is. Also, the baby may gain weight before they begin to grow much taller, or vice versa. You can check the predicted height of your child if you want to plan far into the future!

How to interpret the baby percentile chart?

As mentioned above, raw kilograms are not used when assessing a child's development. However, you always refer to them when calculating the appropriate dose of ibuprofen or paracetamol.

Doctors consider the rate of growth as an important factor when looking at an infant growth chart:

  1. The child should follow the same percentile line on the baby growth chart as they gain weight.
  2. If the results cross two or more percentile lines (they raise/decrease by at least two ranges), e.g. from the 75th-85th percentile to the 15th-25th percentile, you should consult a doctor.
  3. Again, if their weight is below the 5th or above the 95th percentile, check if the baby has always been in those ranges. If your child has only entered these ranges recently, consult a doctor. Also, a visit at a dietitian may be useful - as well as controlling their daily calorie intake.

WHO Growth Chart - an example

Growth Chart WHO (Arne Hendriks, CC BY 2.0,

Our data derives from the WHO (World Health Organization), and the standards were developed using data collected in the WHO Multicentre Growth Reference Study. This tool can be only used if a child is less than five years old. After that age, BMI growth charts become more indicative of a child's development.

Baby weight percentile calculator - how to use it

Let's explain how to use this kids growth chart calculator:

  1. First, give us some details:

    • Age of your child - (either in weeks, months, or even years). The tool is based on a monthly baby weight chart (for kids older than 13 weeks) or by week (for those younger). Note, that the tool provides information only for children up to 5 years old.
    • Whether they're a boy or a girl.
  2. Fill in the weight of your child. You can easily use the in-built weight converter to switch between units.

  3. Get the results.

Now you'll know the answer to the crucial question, "what percentile is my baby?". The first number is the exact baby percentile, and the second is which percentiles they fit into, with an explanation. There's also a graphic explaining where this percentile is with respect to other children.

Weight percentile calculator in practice

It's time to show you how this baby weight percentile calculator works - with an example. Let's take Yvonne, a 31 years old mum of two. The younger one, Vincent, is now five months old. At birth he received 9 out of 10 in the APGAR score, and his development has always seemed normal with both weight and height falling perfectly between the 50 and 75th percentiles.

Two weeks ago, Vincent had a little cold, and Yvonne took him to the pediatrician, who checked his percentiles (with the use of our tool and the WHO growth chart).

The doctor calculated: age: 5 months, sex: male, weight: 6.38 kg. The result was clear, the 8th percentile, exactly between the 5th and 10th percentiles.

What does it mean? Something has changed and the child needs some further diagnostics. The baby percentile chart result itself is quite correct, but as Vincent has dropped by more than 2 percentile lines - his BMI and head circumference percentiles need to be checked.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

Dominika Miszewska

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Weight Percentile Calculator | Correct Child Weight